iwlwifi: mvm: limit maximum queue appropriately

Due to some hardware issues, queue 31 isn't usable on devices that have
32 queues (7000, 8000, 9000 families), which is correctly reflected in
the configuration and TX queue initialization.

However, the firmware API and queue allocation code assumes that there
are 32 queues, and if something actually attempts to use #31 this leads
to a NULL-pointer dereference since it's not allocated.

Fix this by limiting to 31 in the IWL_MVM_DQA_MAX_DATA_QUEUE, and also
add some code to catch this earlier in the future, if the configuration
changes perhaps.

Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20200417100405.98a79be2db6a.I3a4af6b03b87a6bc18db9b1ff9a812f397bee1fc@changeid

drivers/net/wireless/intel/iwlwifi/fw/api/txq.h

@@ -8,7 +8,7 @@
  * Copyright(c) 2007 - 2014 Intel Corporation. All rights reserved.
  * Copyright(c) 2013 - 2015 Intel Mobile Communications GmbH
  * Copyright(c) 2016 - 2017 Intel Deutschland GmbH
- * Copyright(c) 2019 Intel Corporation
+ * Copyright(c) 2019 - 2020 Intel Corporation
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of version 2 of the GNU General Public License as
@@ -31,7 +31,7 @@
  * Copyright(c) 2005 - 2014 Intel Corporation. All rights reserved.
  * Copyright(c) 2013 - 2015 Intel Mobile Communications GmbH
  * Copyright(c) 2016 - 2017 Intel Deutschland GmbH
- * Copyright(c) 2019 Intel Corporation
+ * Copyright(c) 2019 - 2020 Intel Corporation
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -99,7 +99,7 @@ enum iwl_mvm_dqa_txq {
 	IWL_MVM_DQA_MAX_MGMT_QUEUE = 8,
 	IWL_MVM_DQA_AP_PROBE_RESP_QUEUE = 9,
 	IWL_MVM_DQA_MIN_DATA_QUEUE = 10,
-	IWL_MVM_DQA_MAX_DATA_QUEUE = 31,
+	IWL_MVM_DQA_MAX_DATA_QUEUE = 30,
 };
 
 enum iwl_mvm_tx_fifo {

drivers/net/wireless/intel/iwlwifi/mvm/sta.c

@@ -722,6 +722,11 @@ static int iwl_mvm_find_free_queue(struct iwl_mvm *mvm, u8 sta_id,
 
 	lockdep_assert_held(&mvm->mutex);
 
+	if (WARN(maxq >= mvm->trans->trans_cfg->base_params->num_of_queues,
+		 "max queue %d >= num_of_queues (%d)", maxq,
+		 mvm->trans->trans_cfg->base_params->num_of_queues))
+		maxq = mvm->trans->trans_cfg->base_params->num_of_queues - 1;
+
 	/* This should not be hit with new TX path */
 	if (WARN_ON(iwl_mvm_has_new_tx_api(mvm)))
 		return -ENOSPC;